Single crystals of regio-selectively substituted cellulose hetero-esters

Abstract

Lamellar single crystals of some regio-selectively substituted cellulose hetero-esters: cellulose propionate diacetate (CPDA, 2,3-di-O-acetyl-6-O-propionyl cellulose), cellulose acetate dipropionate (CADP, 6-O-acetyl-2,3-di-O-propionyl cellulose), cellulose butyrate diacetate (CBDA, 2,3-di-O-acetyl-6-O-butyryl cellulose) and cellulose acetate dibutyrate (CADB, 6-O-acetyl-2,3-di-O-butyryl cellulose), have been prepared at high temperature in a mixture of dibenzyl ether andn-tetradecane. The CPDA crystals were lozenge-shaped whereas those of CADP, CBDA and CADB had a ribbon morphology. CPDA crystals gave well-resolved electron diffractograms from which the reciprocal lattice parameters a*=0.807 nm−1,b*=0.400 nm−1 andγ*=90° could be determined. Systematic absences occurred at every odd reflection along the two orthogonal axesa*andb*. Thus, the CPDA diffraction pattern is consistent with a pgg symmetry. For CADP, the electron diffraction pattern is consistent with a pmg two-dimensional space group withb the unique axis along the ribbon direction. The diagram yields the reciprocal lattice parameters a* = 0.902 nm−1,b*=0.651 nm−1 andγ*=90°. The CBDA electron diffractogram yields the following cell parameters and two-dimensional space group:a*=0.482 nm−1,b*=0.659 nm−1 andγ*=90°, and a pgg symmetry; and that of CADB:a*=0.834 nm−1,b*=0.645 nm−1 andγ*=90°, and a pmg symmetry.